Focal ablation assembly

ABSTRACT

A focal ablation assembly, used with an endoscope comprising an endoscopic tube, comprises a cryogenic catheter, a balloon and a reinforcing element. The cryogenic catheter is placeable within the endoscopic tube channel and has a distal end placeable at the distal end of the endoscopic tube. The balloon is mountable to the catheter distal end and extends distally of both of the distal ends. The reinforcing element at least partially defines the shape of the balloon in the expanded state. The balloon defines a balloon volume when expanded and has a thermally conductive therapeutic region which provides effectively no thermal insulation. In some examples the focal ablation assembly comprises a delivery catheter extending along the channel with a distal portion fluidly coupled to the balloon interior, whereby refrigerant can be introduced into the balloon interior and towards the therapeutic region by the delivery catheter.

CROSS-REFERENCE TO OTHER APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/180,450 filed on 11 Jul. 2011, now U.S. Pat. No. 9,084,592,(attorney docket WILL 1003-2) which application is incorporated byreference as if fully set forth herein.

This application is related to the following US patent applicationpublication: US 2010/0130970 A1 (attorney docket WILL 1002-2).

BACKGROUND OF THE INVENTION

Throughout the GI tract in the human body there are focal lesions ofunwanted or unhealthy tissue that physicians desire to remove or ablatein situ. Examples of these lesions include ‘islands’ of intestinalmetaplasia and dysplasia in the esophagus or ‘flat’ polyps in the colon.Removal of these tissues through techniques such as Endoscopic MucosalResection (EMR) may create unwanted complications such as bleeding andcurrent ablative modalities such as Argon Plasma Coagulation (APC) andRadio Frequency Ablation (RFA) suffer from a variety of drawbacks.Furthermore, existing cryoablation technologies, which spray the cryogendirectly onto the body lumen do not adequately allow control of theenergy dosage.

BRIEF SUMMARY OF THE INVENTION

An example of a focal ablation assembly is used with an endoscopecomprising an endoscopic tube having proximal and distal ends anddefining a channel extending between the proximal and distal ends. Thefocal ablation assembly comprises a cryogenic catheter, a balloon and areinforcing element. The cryogenic catheter is placeable within thechannel. The cryogenic catheter defines a catheter lumen and has adistal end placeable at the distal end of the endoscopic tube. Theballoon is mountable to at least one of the distal end of the endoscopictube and the distal end of the catheter. The balloon extends distally ofboth of the distal ends of the endoscopic tube and the cryogeniccatheter. The reinforcing element at least partially defines the shapeof the balloon in the expanded state. The balloon defines a balloonvolume when in the expanded state. The balloon comprises a thermallyconductive therapeutic region, the thermally conductive therapeuticregion providing effectively no thermal insulation. In some examples thetherapeutic region comprises a flexible, tissue-conformable therapeuticregion. In some examples the thermal conductivity of the balloon isgreater at the therapeutic region than at a portion of the remainder ofthe balloon. In some examples the focal ablation assembly comprises adelivery catheter extending along the channel with a distal portionfluidly coupled to the balloon interior, whereby refrigerant can beintroduced into the balloon interior and towards the therapeutic regionby the delivery catheter. In some examples the reinforcing elements areformed integrally with the balloon. In some examples the reinforcingelements comprise at least two spaced-apart support wires extending atleast part way along the balloon interior. In some examples thereinforcing elements cause the balloon to have a flattenedcross-sectional shape in the expanded state.

An example of a focal ablation system comprises an endoscope and a focalablation assembly. The endoscope comprises an endoscopic tube havingproximal and distal ends and defines a channel extending between theproximal and distal ends. The focal ablation assembly comprises acryogenic catheter, a balloon, and a reinforcing element. The cryogeniccatheter is located within the channel and defines a catheter lumen. Thecryogenic catheter has a distal end at the distal end of the endoscopictube. The balloon is mounted to the distal end of the catheter with theballoon extending distally of both of the distal ends of the endoscopictube and the cryogenic catheter. The balloon is placeable in collapsedand expanded states and has a balloon interior. The reinforcing elementat least partially defines the shape of the balloon in the expandedstate. The balloon defines a balloon volume when in the expanded state.The balloon comprises a flexible, tissue-conformable, thermallyconductive therapeutic region, the thermally conductive therapeuticregion providing effectively no thermal insulation. Some examples of thefocal ablation system include a delivery catheter extending along thechannel and having a distal portion fluidly coupled to the ballooninterior, whereby refrigerant can be introduced into the ballooninterior and towards the therapeutic region by the refrigerant deliverycatheter. Some examples of the focal ablation system include an exhaustlumen within at least one of (1) the channel of the endoscopic tube, and(2) the catheter lumen.

Other features, aspects and advantages of the present invention can beseen on review the figures, the detailed description, and the claimswhich follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are overall views showing focal ablation systems madeaccording to the invention.

FIGS. 1A-10A are directed to a first type of a focal ablation systemaccording to a first aspect of the invention.

FIGS. 2-10A are a simplified enlarged cross-sectional view of the distalend of one example of the system of FIG. lA showing a cryogenic catheterpassing through the channel of an endoscopic tube with a cap mounted tothe distal end of the endoscopic tube, the cap having a thermallyconductive therapeutic region located at the distal end of the cap.

FIG. 3 is a view similar to that of FIG. 2 of an alternative example ofthe system of FIG. 1A in which the therapeutic region is along asidewall of the cap.

FIG. 4 is a view similar to that of FIG. 2 wherein the cap is mounted tothe distal end of the cryogenic catheter instead of the endoscopic tubeas shown in FIG. 1B.

FIGS. 5A-5C are simplified cross-sectional views of examples of threedifferent caps in which the cross-sectional area of the therapeuticregion at the distal end of each cap is different while thecross-sectional area of the endoscopic tube to which it is mountedremains the same.

FIG. 6 illustrates an example in which the therapeutic region has aconvex outer surface.

FIGS. 7A, 8A and 9A are simplified end views showing caps having round,generally oval and rectangular cross-sectional shapes, respectively,each mounted to the distal end of an endoscope, each Fig. illustrating aconventional endoscope having, in this example, a camera, two lights forillumination and a working channel.

FIGS. 7B, 8B and 9B show the caps of FIGS. 7A, 8A and 9A having distalends oriented perpendicular to the centerlines of the respective caps.

FIGS. 7C, 8C and 9C show the caps of FIGS. 7A, 8A and 9A having distalends oriented obliquely to the centerlines of the respective caps.

FIG. 10 shows an example of a cap similar to the cap of FIG. 2 but inwhich the cap has an extension defining an exhaust lumen coaxial withthe endoscopic tube.

FIG. 10A is a view along line 10A-10A of FIG. 10.

FIGS. 11-15 show balloon-type of focal ablation systems according to asecond aspect of the invention.

FIG. 11 shows an example of a balloon type focal ablation system inwhich an elastomeric balloon is mounted to the distal end of thecryogenic catheter and expands within the cap, a portion of the balloonforming a barrier to the refrigerant along the therapeutic region at thedistal end of the cap.

FIGS. 12 and 12A are simplified side and end cross-sectional views of aballoon type focal ablation system in which a balloon type focalablation assembly is used with an endoscopic tube, the balloon beingmounted to the distal end of a cryogenic catheter, the cryogeniccatheter passing through the channel of the endoscopic tube, thetherapeutic region being along a sidewall of the balloon. FIG. 12A showsthe use of reinforcing elements within the balloon to cause the balloonto have a flattened or oval cross-sectional shape to better conform tothe sidewall of the body lumen.

FIGS. 13 and 13A are simplified side and end cross-sectional views of afocal ablation balloon and reinforcing elements similar to those ofFIGS. 12 and 12A.

FIG. 14 illustrates another example of a balloon type focal ablationsystem in which the distal end of a reinforcing element extends throughthe delivery catheter and is secured to the distal portion of theballoon.

FIG. 15 shows a further example of a balloon type focal ablation systemcomprising a balloon type cap.

DETAILED DESCRIPTION OF THE INVENTION

The following description will typically be with reference to specificstructural embodiments and methods. It is to be understood that there isno intention to limit the invention to the specifically disclosedembodiments and methods but that the invention may be practiced usingother features, elements, methods and embodiments. Preferred embodimentsare described to illustrate the present invention, not to limit itsscope, which is defined by the claims. Those of ordinary skill in theart will recognize a variety of equivalent variations on the descriptionthat follows. Like elements in various embodiments are commonly referredto with like reference numerals.

The control of three primary factors is necessary for repeatablecryoablation via evaporative cooling. These factors are evaporationtemperature of the cryogen, the mass flow rate of the cryogen/surfacearea, and the amount of time that the cryogen is applied. The presentinvention directly addresses two of these factors. (1) Evaporationtemperature of the cryogen is set by controlling the evaporationpressure. The evaporation pressure can be controlled by appropriatelysizing the cryogenic refrigerant delivery and exhaust lumens. (2) Themass flow rate/surface area can be controlled by appropriately sizingthe cryogenic refrigerant delivery lumen (to control mass flow rate) anddefining a fixed treatment area either by physically defining atreatment area or by controlling distribution of the cryogen deliveryonto a treatment surface.

FIG. 1A is an overall view showing a generalized example of a focalablation system 10 including broadly an endoscope 12 and a focalablation assembly 14. Endoscope 12 includes an endoscopic tube 16 havingan accessory channel port 18 at a proximal end 20 of endoscopic tube 16and a cap 22 at the distal end 24 of endoscopic tube 16. Endoscope 12may be a conventional endoscope such as Olympus GIF-140 or GIF-Q160Z,that connects to an image processor 19, which then displays the image onmonitor 21. FIG. 1B is similar to FIG. 1A but shows cap 22 mounted tothe distal end 34 of cryogenic catheter 26 instead of endoscopic tube16.

FIGS. 2-12 are directed to a first type of a focal ablation system 10according to a first aspect of the invention. Focal ablation assembly14, see FIGS. 1 and 2, includes a cap 22 mounted to the distal end 24 ofan endoscopic tube 16 and a cryogenic catheter 26 passing through thechannel 28 of endoscopic tube 16. Focal ablation assembly 14 alsoincludes a cryoablation controller 25 at the proximal end of 27 ofcryogenic catheter 26. In some examples, described below with referenceto FIGS. 1B and 4, cap 22 can be mounted to the distal end 34 ofcryogenic catheter 26. Cap 22 in FIG. 2 has a generally cylindricalcross-sectional shape and defines a centerline 30. Cap 22 has a distalend 32 extending distally of the distal end 24 of endoscopic tube 16 andthe distal end 34 of cryogenic catheter 26. In this example cap 22 isoriented obliquely to centerline 30 to facilitate tissue apposition.Cryogenic catheter 26 defines a catheter lumen 29 through which adelivery catheter 31 passes. As is discussed in more detail below,distal end 32 of cap 22 will be placed against tissue at the target siteto be treated.

Cap 22 is preferably of a clear, semi-rigid, soft, flexible material, ora combination of materials, such as a polymer material, so tosubstantially maintain its shape during use while not causing tissuetrauma. Examples of the material for 22 include silicone, polyurethane,polyvinyl chloride, and C-Flex®, a thermoplastic elastomer, specificallystyrene-ethylene-butylene modified block copolymer with silicone oil.Cap 22 may be manufactured by, for example, injection molding, casting,or thermoforming. Distal end 32 of cap 22 defines a thermally conductivetherapeutic region 36 having a typical cross-sectional area of 0.5 cm²to 3.0 cm². In this example therapeutic region 36 is covered by a cover38 of a thin transparent polymer, such as polyurethane having athickness of typically less than 0.05 mm (0.002 inch). In this way theliquid refrigerant 40 passing through the delivery lumen of deliverycatheter 31 and out through the exit opening 41 of delivery catheter 31does not contact tissue outside the target site but rather heat isremoved from the tissue at the target site as the liquid refrigerantevaporates while in contact with cover 38. Although polyurethane may notbe considered to be highly thermally conductive, the thinness of cover38 allows cover 38 to provide effectively no thermal insulation betweenthe evaporating liquid refrigerant and the target tissue. In addition,it is preferable that cover 38 be transparent or at least translucent sothat the physician can see what is happening to the tissue at the targetsite. The selection of the size of therapeutic region 36 is typicallychosen according to the size of the treatment site or the desired massflow rate/surface area for refrigerant 40, or both. Evaporatedrefrigerant 42 passes out of cap volume 39 through catheter lumen 29between delivery catheter 31 and the inner wall of cryogenic catheter26.

Cover 38 is stated to provide effectively no thermal insulation betweenthe evaporating liquid refrigerant and the target tissue. In thisapplication the phrase effectively no thermal insulation is meant tomean that tissue necrosis can occur at the target site upon theapplication of a cryogenically ablative liquid refrigerant, such asnitrous oxide (N₂O), to the surface of cover 38.

Cryogenic catheter 26 may be sized appropriately for introductionthrough, for example, 2.0 mm, 2.8 mm or 3.7 mm diameter instrumentchannels 28. Cryogenic catheter 26 may be constructed from materialssuch as PEBAX or nylon. Delivery catheter 31 may be constructed from arigid polymer such as polyimide or a metal such as stainless steel,sufficient to withstand internal pressure approaching 1000 psig. Thediameter of delivery lumen 44 defined by delivery catheter 31 istypically in the range of 0.15 mm (0.006 inch) to 0.30 mm (0.012 inch).The diameter of delivery lumen 44 can be chosen according to the desiredmass flow rate/surface area for refrigerant 40 contacting therapeuticregion 36.

FIG. 3 is a view similar to that of FIG. 2 of an alternative example ofthe focal ablation system 10 of FIG. 1 in which the therapeutic region36 is along a sidewall 46 of the cap. Delivery catheter 31 extendscompletely through cap volume 39 and is secured to a distal end of cap22. Delivery catheter 31 has a laterally oriented exit opening 41positioned opposite the therapeutic region 36 along sidewall 46 of cap22. This feature permits liquid refrigerant 40 to be directed againstsidewall 46 at therapeutic region 36 so the target tissue at the targettreatment site 78 against which therapeutic region 36 is pressing, seeFIG. 12, can be thermally ablated due to the low temperature of theliquid refrigerant.

FIG. 4 is a view similar to that of FIG. 2 wherein the cap 22 is mountedto the distal end 34 of the cryogenic catheter 26 instead of theendoscopic tube 16. See also FIG. 1B.

FIGS. 5A-5C are simplified cross-sectional views of examples of threedifferent caps 22 in which the cross-sectional area 48 of thetherapeutic region 36 at the distal end 32 of each cap 22 is differentwhile the cross-sectional area 50 of the endoscopic tube 16 to which itis mounted remains the same. This concept is used to allow the physicianto choose the appropriately sized cap 22 according to the size of thetarget site, or the mass flow rate/surface area of refrigerant 40, orboth.

FIG. 6 illustrates an example in which the therapeutic region 36 has aconvex outer surface 52. This configuration may be useful to improve theamount of contact between the therapeutic surface of the cap and thetarget tissue. FIGS. 7A, 8A and 9A are simplified end views showing caps22 having round, generally oval and rectangular cross-sectional shapes,respectively. Each cap 22 is mounted to the distal end 24 of anendoscopic tube 16. Each figure illustrates a conventional endoscope 12having, in this example, a camera 53, two lights 54 for illumination anda working channel 28.

FIGS. 7B, 8B and 9B show the caps 22 of FIGS. 7A, 8A and 9A havingdistal ends 32 oriented perpendicular to the centerlines 30 of therespective caps. FIGS. 7C, 8C and 9C show the caps 22 of FIGS. 7A, 8Aand 9A having distal ends 32 oriented obliquely to the centerlines 30 ofthe respective caps.

FIGS. 10 and 10A show an example of cap 22 similar to the cap 22 of FIG.2 but in which an exhaust lumen 56 is defined by a coaxial extension 58of cap 22. Extension 58 will lie generally parallel to the endoscopictube 16. This permits a larger cross-sectional area for the exhaustlumen than would be typically available if the exhaust lumen was definedby an accessory channel of endoscopic tube 16. Exhaust lumen 56 istypically in the range of 2-5 mm in diameter. The cross-sectional areasprovided by catheter lumen 29 when used as exhaust lumens in the aboveexamples are typically of a similar size.

FIG. 11 shows another example in which an elastomeric balloon 60 ismounted to the distal end 34 of the cryogenic catheter 26. Balloon 60expands within the cap volume 39 of cap 22 with a portion 62 of theballoon forming the cover 38 along the therapeutic region 36 at thedistal end 32 of the cap. A vent hole 63 is formed in the sidewall 46 ofcap 22 to facilitate the expansion of balloon 60.

In use, the physician will typically select a cap 22 having theappropriate size and shape for the particular target treatment site 78.The size of therapeutic region 36 may also be chosen according to thedesired mass flow rate/surface area for refrigerant 40. Assuming thefocal ablation system 10 of FIG. 2 is being used, cap 22 can beinstalled on the distal end 24 of endoscopic tube 16. Cryogenic catheter26, typically with delivery catheter 31 therein, can be placed throughaccessory port 18 of the endoscope 12 and passes through channel 28 ofthe endoscopic tube 16 until the distal end 34 of cryogenic catheter 26is at cap volume 39. Note that the installation of cap 22 could occurafter positioning cryogenic catheter 26 within endoscope 12. The distalportion of focal ablation system 10 is placed in the patient so thatregion 36 is properly positioned at the target treatment site 78. Therefrigerant from cryoablation controller 25 is then directed throughdelivery catheter 31 and against cover 38 at to the target treatmentsite 78. The evaporation of the refrigerant on cover 38 lowers thetemperature of the tissue at the target treatment site enough to causenecrosis of the tissue. The evaporated refrigerant 42 passes out of capvolume 39 through catheter lumen 29.

FIGS. 12-15 show balloon type of focal ablation systems, somewhatdifferent from the focal ablation system of FIGS. 1-11, according to asecond aspect of the invention.

FIGS. 12 and 12A are simplified side and end cross-sectional views of aballoon type focal ablation system 70 in which a balloon type focalablation assembly 72 is used with an endoscopic tube 16 of an endoscope12. A balloon 74 is mounted to the distal end 34 of cryogenic catheter26. The cryogenic catheter 26 extends through the channel 28 ofendoscopic tube 16. The therapeutic region 36 is along a sidewall 76 ofballoon 74. In this example cryogenic catheter 26 has a dogleg shapedistal portion to facilitate placement of therapeutic region 36 alongsidewall 76 and against a target treatment site 78 of the body structure80. Delivery catheter 82 passes through lumen 29 with its distal end 84secured to the distal end 86 of balloon 74. Delivery catheter 82 has, inthis example, a number of laterally directed exit openings 41 acting asdelivery ports to direct liquid refrigerant 40 into the interior 85 ofballoon 74 and against sidewall 76 of balloon 74 at target site 78. Thesize, number and positions of openings 41 can be chosen according to thesize of the target treatment site 78 and desired mass flow rate/surfacearea for refrigerant 40. FIG. 12A shows the use of reinforcing elements88, such as nitinol support wires, within the balloon 74 to cause theballoon to have a flattened or oval cross-sectional shape to betterconform to the shape of the body structure 80. The use of reinforcingelements 88 also helps to maintain balloon 74 in direct contact with thebody structure during the procedure.

FIGS. 13 and 13A are simplified side and end cross-sectional views of afocal ablation balloon 74 and reinforcing elements 88 similar to thoseof FIGS. 12 and 12A.

FIG. 14 illustrates another example of a balloon type focal ablationsystem 70 in which the distal end of the reinforcing element 88 extendsthrough the delivery catheter 31. The distal end 90 of reinforcingelement 88 is secured to the central portion of the working region 36 ofballoon 74 in the following manner. Balloon 74 has a stem portion 92 atthe center of therapeutic, working region 36 extending inwardly into thevolume 93 defined by the balloon. A thermally conductive filler material94 is used to secure distal end 90 of reinforcing element 88 to stemportion 92. As indicated by liquid refrigerant arrows 40, liquidrefrigerant is directed toward the center of working region 36surrounding stem portion 92.

FIG. 15 shows an example of a balloon type focal ablation systemcomprising a balloon type cap 98, which is not generally rigid as caps22 in the examples above FIGS. 1-11. Rather, cap 98 is typically made ofone or more materials similar to those used with balloon 74 and includesreinforcing elements 88, not shown in FIG. 15, which may be made of, forexample, a metal, such as nitinol, or of the same material as the restof cap 98. Cap 98 also includes a cover 38, typically made of a thinfilm of silicone, polyurethane, or PET. As with the balloon type focalablation systems 70 of FIGS. 12-14, the full expansion of cap 98 istypically the result of reinforcing elements 88 and the internalpressure created by the vaporization of refrigerant 40 and expansion dueto the creation of exhaust gas 42.

In the use of the focal ablation system 70 of FIGS. 12-13A, thephysician will typically select a focal ablation assembly 72 including aballoon 74 having the appropriate size and shape for the particulartarget treatment site 78. Cryogenic catheter 26, typically with deliverycatheter 82 therein and the balloon 74 at the distal end 34, can beplaced through accessory port 18 of the endoscope 12 and pass throughchannel 28 of the endoscopic tube 16 until sidewall 76 of balloon 74 isadjacent to therapeutic region 36 of body structure 80. The refrigerant40 from cryoablation controller 25 is then directed through deliverycatheter 82 and against balloon sidewall 76 at to the target treatmentsite 78. The evaporation of the refrigerant on sidewall 76 of balloon 74lowers the temperature of the tissue at the target treatment site 78enough to cause necrosis of the target tissue. The evaporatedrefrigerant 42 passes out of the interior of balloon 74 through catheterlumen 29. The use of the examples of FIGS. 14 and 15 are carried out insimilar manners with the working region 36 positioned at targettreatment site 78.

The above descriptions may have used terms such as above, below, top,bottom, over, under, et cetera. These terms may be used in thedescription and claims to aid understanding of the invention and notused in a limiting sense.

While the present invention is disclosed by reference to the preferredembodiments and examples detailed above, it is to be understood thatthese examples are intended in an illustrative rather than in a limitingsense. It is contemplated that modifications and combinations will occurto those skilled in the art, which modifications and combinations willbe within the spirit of the invention and the scope of the followingclaims. For example, cryogenic catheter 26 may also contain featuresrelated to measuring the performance of the system for either safety orefficacy reasons. Examples of these features include a pressure sensinglumen for monitoring pressure in the volumes 39, 93, and a temperaturesensing device (e.g. thermistor or thermocouple) for monitoringtemperature in the cap 22, especially at working region 36.

Any and all patents, patent applications and printed publicationsreferred to above are incorporated by reference.

What is claimed is:
 1. A focal ablation assembly, adapted for use withan endoscope within a hollow body structure, the hollow body structurehaving a target site at an inner surface thereof and a target sitecross-sectional area at the target site, the endoscope comprising anendoscopic tube having proximal and distal ends and defining a channelextending between the proximal and distal ends, the focal ablationassembly comprising: a cryogenic catheter placeable within the channel,the cryogenic catheter defining a catheter lumen and having a distal endplaceable at the distal end of the endoscopic tube; a balloon mountableto the distal end of the cryogenic catheter, the balloon extendingdistally of both of the distal ends of the endoscopic tube and thecryogenic catheter; the balloon placeable in collapsed and expandedstates, the balloon having a balloon interior and a balloon sidewall,the sidewall having a thermally conductive therapeutic region providingeffectively no thermal insulation; a balloon-shape-affecting reinforcingelement located within the balloon interior; with the balloon in theexpanded state at the target site, the reinforcing element comprisingspaced apart elements (1) placing the balloon into a flattenedconfiguration to better conform to the hollow body structure, and (2)helping to maintain the therapeutic region in direct contact with thehollow body structure; and the cross-sectional area of the balloon whenthe balloon is in the flattened configuration at the target site beingsubstantially greater than the target site cross-sectional area.
 2. Theassembly according to claim 1, wherein the spaced apart elementscomprise at least two spaced-apart support wires extending at least partway along the balloon interior.
 3. The assembly according to claim 1,wherein the balloon is made of an elastomeric material.
 4. The assemblyaccording to claim 1, wherein the thermal conductivity of the balloon isgreater at the therapeutic region than at least a portion of theremainder of the balloon.
 5. The assembly according to claim 1, whereinthe endoscopic tube has a centerline and the therapeutic region isoriented oblique to the centerline when the cryogenic catheter islocated within the endoscopic channel.
 6. The assembly according toclaim 1, wherein the therapeutic region is generally elliptical.
 7. Theassembly according to claim 1, wherein the therapeutic region has across-sectional area and the endoscopic tube has a cross-sectional area,the cross-sectional area of the therapeutic region being greater thanthe cross-sectional area of the endoscopic tube when the balloon is inthe flattened configuration.
 8. The assembly according to 1, furthercomprising a delivery catheter extendable along the channel and having adistal portion fluidly coupled to the balloon interior, wherebyrefrigerant can be introduced into the balloon interior and towards thetherapeutic region by the delivery catheter.
 9. The assembly accordingto claim 8, wherein the refrigerant delivery catheter extends throughthe cryogenic catheter.
 10. The assembly according to claim 8, furthercomprising an exhaust lumen defined by the catheter lumen.
 11. Theassembly according to claim 8, further comprising an exhaust lumenadapted for use within at least one of (1) the channel of the endoscopictube, and (2) the catheter lumen.
 12. The assembly according to claim 8,wherein the distal portion of the delivery catheter has multiple exitopenings for the discharge of the refrigerant into the balloon andtowards the therapeutic region.
 13. A focal ablation assembly, adaptedfor use with an endoscope within a hollow body structure, the hollowbody structure having a target site at an inner surface thereof and atarget site cross-sectional area at the target site, the endoscopecomprising an endoscopic tube having proximal and distal ends anddefining a channel extending between the proximal and distal ends, thefocal ablation assembly comprising: a cryogenic catheter placeablewithin the channel, the cryogenic catheter defining a catheter lumen andhaving a distal end placeable at the distal end of the endoscopic tube;a balloon mountable to the distal end of the cryogenic catheter, theballoon extending distally of both of the distal ends of the endoscopictube and the cryogenic catheter; the balloon placeable in collapsed andexpanded states, the balloon having a balloon interior and a balloonsidewall, the sidewall having a thermally conductive therapeutic regionproviding effectively no thermal insulation; a balloon-shape-affectingreinforcing element located within the balloon interior; with theballoon in the expanded state at the target site, the reinforcingelement comprising: means for placing the balloon into a flattenedconfiguration to better conform to the hollow body structure; and meansfor helping to maintain the therapeutic region in direct contact withthe hollow body structure; and the cross-sectional area of the balloonwhen the balloon is in the flattened configuration at the target sitebeing substantially greater than the target site cross-sectional area.